This invention relates to a tape cassette and, more particularly, to a video cassette dust door latch having inherent spring action.
For convenience of reference, when describing the tape cassette of the prior art and the present invention, "inward" means in a direction toward to the interior of the cassette from its sides, "outward" means in a direction toward the sides of the cassette from the interior, "upward" means in a direction toward the cassette cover from the cassette base, and "downward" means in a direction toward the base from the cover.
A conventional tape cassette usually has a flat, substantially rectangular, configuration which may be formed of a suitable plastic, and includes a cassette cover and base, each having side walls. Tape reels are usually located in side-by-side relation within the cassette so as to be freely rotatable, and magnetic tape is wound between the tape reels.
Such cassettes also usually include a hinged dust door and a biased latch for temporarily locking the dust door closed. The dust door protects the tape in the cassette from dust, abrasion, etc., when the cassette is not being used in a tape player/recorder, e.g., during transport and storage.
Conventionally, the latch has been made in the form of a substantially flat, rectangular latch body, pivotably supported by lateral pivot pins which rest in the cassette base. The latch body is urged outwardly by a spring attached to the latch body and abutting a wall of the cassette. First and second projections on the outward side surface of the latch body extend through corresponding openings formed in the side wall of the cassette base. The first projection engages an opening in the side of the dust door when the door is in a closed position, thereby locking the door. The second projection is exposed on the outside of the tape cassette, adjacent one end of the dust door, to allow access by a movable pin on the tape player/recorder when the tape cassette is inserted into the tape player/recorder. The second projection is automatically depressed by the pin, the latch pivots against the force of the spring, releasing the first projection is released from engagement with the dust door, and the dust door is allowed to open to expose the tape to the tape player/recorder.
One type of spring conventionally used to bias the latch is a separate, coil spring connected to a boss formed to extend from the latch body, as described in Assignee's U.S. Pat. No. 4,475,700. The drawbacks associated with this type of latch/spring assembly are the cost associated with manufacturing and assembling multiple parts and the difficulty of handling, attaching and preloading the coil spring. The present invention is not directed to this type of separate spring, but is directed to a type wherein the latch is characterized by inherent spring action.
A dust door latch having a spring integrally formed therewith has been proposed. More particularly, as described in U.S. Pat. No. 4,323,207, issued to Gebeke, the latch includes an integral spring in the form of a "U" or "S"-shape extending from a rigid body portion slidably mounted in a housing of the cassette body. However, this structure is sensitive to precise molding and how it is located in the cassette. For example, the spring extension must be carefully preloaded or it could be dislodged and not operate. This latch design is also vulnerable to storing and shipping damage.
Further, U.S. Pat. No. 4,466,583, issued to Giannis et al., discloses, as shown in FIG. 1 herein, a dust door latch generally designated by element 10. The latch 10 is mounted for rotational movement about a substantially horizontal axis "a" between a latching position at which the latch 10 locks the dust door (not shown) in its closed position, and an unlatching position in which the dust door is unlatched for opening. The rotational movement is provided by a pair of well-known, cylindrical pivot pins 12 and 14. Pivot pin 12 rests in a rounded notch 16 in a forward wall 18 of the cassette base 20. The other pivot pin 14 rests in another rounded notch 22 on the top of an interior wall 24 which extends upwardly from the bottom wall 26 of the cassette base 20. The usual operable projections described above (not shown) extend outwardly from the latch 10 through openings (one shown at 36) formed in the cassette base 20 side wall 38. The cassette base also includes a conventional light hole 40. An elongated resilient arm 28 is formed on the latch 10 to extend downwardly or upwardly toward the interior of the cassette base 20 and in the direction of rotation of the latch 10 toward its unlatched position. Arm 28 is attached at one end 30 to the latch 10 in an integral, one-piece relationship. The opposite end 32 of arm 28 must be pre-loaded, i.e., biased against an inner wall 34 of the cassette base 20 for normally urging the latch 10 toward its latching position.
The drawbacks associated with this conventional, integral dust door latch/spring 10 are that: (a) it is costly to produce since the arm 28 must be carefully molded to ensure proper installation and retention of its biasing ability over time and under different temperature conditions; (b) assembly of this small part is difficult due to the need to bend the arm 28 toward the latch 10 during assembly to prevent obstruction with the wall 34 and to properly preload the spring 28 in the cassette base 20 against the wall 34; (c) the pivot pins 12, 14 must be accurately molded and received by the notches 16, 22 or else the latch 10 will not pivot as required, and the dust door will not open; (d) the mold for forming the latch 10 must be able to accurately form the spring arm 28 to extend from a central planar portion; and (e) the mold to form the cassette base must be able to form the separate wall 34 to allow preloading of the spring arm 28.
Further, as with any mass-produced, consumer item such as video cassettes, there is always a desire to eliminate parts and assembly steps to decrease overall cost.
Although the prior art described above eliminates some of the problems inherent in the tape cassette door latch art, the prior art still does not teach a biased door latch capable of the most cost efficient production nor the most time efficient automated assembly, nor does it ever have to be preloaded.